Question

How do you multiply `(8-2i)(-3+7i)` in trigonometric form?

Answer 1

FOIL

Explanation:

If it was `(8-2x)(-3+7x)`

You would foil, and you would do that same thing.
Now, lets foil with `i`.

1. First `(8*-3)=-24`

2. Outer `(8*7i) = 56i`

   • Act `i` like `x`

3. Inner `(-2i*-3)=6i`

4. Last `(-2i*7i)=-14i^2=-14*-1=14`

   • Remember #i^2 = -1

Now put it all back together
`-24+56i+6i+14`

Combine like terms
`-10+62i`